1. Field of the Invention
The present invention is directed to a clutch assembly, particularly for a friction clutch of a motor vehicle, with at least one clutch housing in which a diaphragm spring is arranged that acts on a pressure plate, or clutch cover, and secured to the clutch housing by a holding ring with retaining tabs distributed over the circumference at a distance axially from the holding ring. The retaining tabs are arranged so as to define an axial stop. A spring element is arranged between two adjacent structural component parts of the clutch assembly arranged between the holding ring and the axial stop of the retaining tabs, this spring element exerting an axial spring force on the adjacent structural component parts.
2. Description of the Related Art
In devices of the type mentioned above, the diaphragm spring supports become worn over the lifespan of the clutch when the pressure plates are actuated by pressure, particularly pressure plates in vehicle friction clutches. The release travel of the pressure plate is reduced through this wear. If the expected amount of wear is allowed for in the design of the clutch, the release travel in the new clutch is greater by the amount of wear than is actually necessary. This results in an unfavorable gear ratio and poor efficiency with correspondingly high releasing force.
On the other hand, if the wear is not taken into account, the space resulting between the diaphragm spring and the surrounding structural component parts owing to wear reduces the release travel of the pressure plate. One result of the reduced release travel may be a malfunctioning of the pressure plate, i.e., the clutch can no longer be separated. However, at the same time, this means that it is no longer possible to change gears so that the motor vehicle must be towed in some cases.
Therefore, it has been proposed in the prior art to compensate for the wear of the supports by preloaded resilient elements in the form of an annular spring with axial raised portions or a disk spring. In pressure plates with a holding ring, this disk spring is inserted above the housing under the tabs of the holding ring so that the spring is preloaded when assembled. When wear occurs, the disk spring relaxes by a corresponding amount and accordingly compensates for the wear.
DE 102007053724 and DE 102007053161 suggest a clutch device in which an annular spring element is inserted between the holding element and the clutch housing or between the holding element and the diaphragm spring. The spring element has portions that are offset axially relative to one another and which exert an axial force on the surrounding structural component parts.
Further, it is known from GB 1 511 745 to construct the holding element in such that it possesses a characteristic resembling that of a disk spring so that wear can be compensated in an analogous manner.
However, these solutions are disadvantageous in that the springs are very costly to produce, particularly when care must be taken to place them in the exact wanted circumferential position. Assembly costs are also relatively high because the fabricated springs must be handled with precision during assembly in order to achieve the correct final assembly position. Further, the spring deflection provided by the annular springs is usually too small.